-1600 + 2 = -1598
-800 + 4 = -796
-640 + 5 = -635
-400 + 8 = -392
-320 + 10 = -310
For tidiness, printing of 18 lines which failed to find two such factors, was suppressed
Observation : No two such factors can be found !!
Conclusion : Trinomial can not be factored